Training tips for the roundhouse kick needed.

Hi

I was hoping if someone could advise me with some training tips on how to improve the height of my round house kicks. I can kick up to head level with most of my other kicks, but when comes to the round house I struggle with kicking higher then my opponents stomach. As the round house is the main weapon in sparring this problem makes my game rather limited as I can't use it for threatening my opponents head and makes me slower to deliver the ones aimed for the stomach.

Yeah, I actually did. Very nice thread and I think his advice on trying to do the techniques first slowly and then fast is very good. I've also been trying to do that for strikes and blocks to try and get the little things right.
I think one of my problem lies in not knowing which are the best stretches. I've been trying to do some of the stretch kick techniques at home in my spare time, but I think I'm not doing the side one correctly as I often get pains in my hip when trying to do them, especially for my left leg. I'm also not sure which are the best static stretches for improving the roundhouse. I've been trying to use Google, but usually end up on sites where people are trying to sell me something.
One the technical side I think I need to focus on bringing my knee up higher and tilting backwards before I finish the kick.

Can't you just ask your instructors for the best stretching methods ( because they can give you a demonstration)?? Or if you're not sure if you're doing things right, can't you just ask the instructors if it's normal to get pain in the hip while you're doing this n that?

Dynamic stretching is your friend. Also, work on opening your hips up while kicking. If your pelvis is not PERPENDICULAR to your opponent when you are kicking then you aren't getting your hip around far enough for a good high kick. Also, point your knee as high up as you can on the chamber, the higher your chamber is the higher your kick is going to end up.
You can also lean back slightly to help increase the kick height, just be sure you aren't off-balancing yourself.

What Kintanon said.
Basically the best way to just warm up, do some dynamic stretching (make sure you know the difference between that and ballistic stretching!), do some regular training, then if you fancy do some isometric stretching at the end of the workout before cooling down with some static stretching. Wash, rinse, repeat. Doing the dynamic stretching will help you far more than trying to sit in a forced stretch.